Circuit board and method for manufacturing the same

ABSTRACT

A circuit board with conductive wiring which is precisely shaped and sized includes a two-part conductive element, namely a first conductive wiring layer and a second conductive wiring layer. The first conductive wiring layer and the second conductive wiring layer are in direct contact to each other. A projection of the first conductive wiring layer along a direction perpendicular to the circuit board and a projection of the second conductive wiring layer totally cover each other.

FIELD

The subject matter herein generally relates to a circuit board and amethod for manufacturing the circuit board.

BACKGROUND

Circuit boards are widely used in various kinds of electronic devices.The circuit board may have a thick copper layer, which can provide animproved conductivity between electronic elements. However, a coppersubstrate needs to be etched for a long time to form the thick copperlayer, which may also cause the copper substrate to be etched laterally.Thus, a line space and a line width of the thick copper layer need to beincreased. However, the circuit board with a large line space and alarge line width is not desirable. Improvement in the art is preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures.

FIG. 1 is a flowchart of an exemplary embodiment of a method formanufacturing a circuit board.

FIG. 2 is a diagram of a metal substrate, a first dry film, and a seconddry film used in the method of FIG. 1.

FIG. 3 is a diagram showing the first dry film and the second dry filmbeing formed on the metal substrate of FIG. 2.

FIG. 4 is a diagram showing the first dry film and the second dry filmof FIG. 3 being treated by an exposure process.

FIG. 5 is a diagram showing the first dry film of FIG. 4 being treatedby a development process to form a hollow pattern.

FIG. 6 is a diagram showing a first conductive wiring layer being formedin the hollow pattern of FIG. 5.

FIG. 7 is a diagram showing the first dry film and the second dry filmof FIG. 6 being removed.

FIG. 8 is a diagram showing a first cover film being formed on the firstconductive wiring layer of FIG. 7.

FIG. 9 is a diagram showing a third dry film being formed on the metalsubstrate of FIG. 8.

FIG. 10 is a diagram showing third dry film of FIG. 9 being treated byan exposure process.

FIG. 11 is a diagram showing a second conductive wiring layer beingformed on the third dry film of FIG. 10.

FIG. 12 is a diagram showing a second cover film being formed on thesecond conductive wiring layer of FIG. 11 to form a circuit board.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale and the proportions of certain parts may beexaggerated to better illustrate details and features of the presentdisclosure.

The term “comprising,” when utilized, means “including, but notnecessarily limited to”; it specifically indicates open-ended inclusionor membership in the so-described combination, group, series, and thelike.

Referring to FIG. 1, a method for manufacturing a circuit board 100 (seeFIG. 12) is presented in accordance with an exemplary embodiment. Themethod for manufacturing the circuit board 100 is provided by way ofexample, as there are a variety of ways to carry out the method. Theexemplary method can begin at block 201.

At block 101, referring to FIG. 2, a metal substrate 10, a first dryfilm 20, and a second dry film 30 are provided. The metal substrate 10comprises a first surface 12 and a second surface 14 facing away fromthe first surface 12.

In at least one exemplary embodiment, the metal substrate 10 is made ofmetal or metal alloy, and can be made by cutting a copper block. Themetal substrate 10 has a thickness of about 50 μm to about 80 μm. In atleast one exemplary embodiment, the metal substrate 10 has a thicknessof about 70 μm.

In at least one exemplary embodiment, the first dry film 20 and thesecond dry film 30 have a similar structure. Each of the first dry film20 and the second dry film 30 comprises a polyester layer, a photoresistlayer, and a polyethylene layer (not shown) stacked together. The firstdry film 20 has a thickness greater than a thickness of the second dryfilm 30. In at least one exemplary embodiment, the first dry film 20 hasa thickness of about 75 μm. The second dry film 30 has a thickness ofabout 15 μm.

At block 102, referring to FIG. 3, the first dry film 20 and the seconddry film 30 are respectively formed on the first surface 12 and thesecond surface 14.

At block 103, referring to FIG. 4, the first dry film 20 and the seconddry film 30 are treated by an exposure process.

In at least one exemplary embodiment, the exposure can be carried out bycovering a photo mask (not shown) on the first dry film 20 facing awayfrom the metal substrate 10, and exposing the first dry film 20 and thesecond dry film 30 to ultraviolet radiation, thereby causing the seconddry film 30 and an uncovered portion of the first dry film 20 to beexposed under the ultraviolet radiation and be solidified.

At block 104, referring to FIG. 5, the first dry film 20 and the seconddry film 30 after the exposure process are treated by a developmentprocess, thereby forming a hollow pattern 22 in the first dry film 20towards the first surface 12.

In at least one exemplary embodiment, the development can be carried outby removing the photo mask, and etching a remaining portion of the firstdry film 20 that is not exposed, thereby forming the hollow pattern 22in the first dry film 20. In at least one exemplary embodiment, thefirst dry film 20 is etched by a sodium hydroxide solution having a massconcentration of about 1%.

At block 105, referring to FIG. 6, the metal substrate 10 iselectroplated to form a first conductive wiring layer 24 in the hollowpattern 22.

In at least one exemplary embodiment, the first conductive wiring layer24 has a thickness of about 60 μm to about 70 μm. The electroplating canbe panel plating that does not require any lead wire and has asimplified process.

At block 106, referring to FIG. 7, the first dry film 20 and the seconddry film 30 are removed, thereby exposing a remaining portion of thefirst surface 12.

The cross-sectional shape of the first conductive wiring layer 24 can bevaried as needed. In at least one exemplary embodiment, thecross-sectional shape of the first conductive wiring layer 24 issubstantially rectangular.

At block 107, referring to FIG. 8, a first cover film 40 is covered onand fills in gaps of the first conductive wiring layer 24.

In at least one exemplary embodiment, the first cover film 40 comprisesa first cover layer 42 and a first adhesive layer 44 connected to thefirst cover layer 42. The first adhesive layer 44 is between the firstcover layer 42 and the first conductive wiring layer 24 and fills ingaps of the first conductive wiring layer 24. The first cover film 40can be made of liquid crystal polymer (LCP).

At block 108, referring to FIG. 9, a third dry film 50 is covered on thesecond surface 14.

The third dry film 50 can have a similar structure as the first dry film20 and the second dry film 30. In at least one exemplary embodiment, thethird dry film 50 has a thickness the same as that of the second dryfilm 30.

At block 109, referring to FIG. 10, the third dry film 50 is treated byan exposure process to form patterns corresponding to the firstconductive wiring layer 24.

At block 110, referring to FIG. 11, the metal substrate 10 is treated bya development process through the patterned third dry film 50, therebycompletely etching a portion of the metal substrate 10 from the secondsurface 14 to the first surface 12, to form a second conductive wiringlayer 16. Then the third dry film 50 is removed.

The second conductive wiring layer 16 is directly and electricallyconnected to the first conductive wiring layer 24. A projection of thefirst conductive wiring layer 24 along a direction perpendicular to thecircuit board 100 and a projection of the second conductive wiring layer16 totally cover each other. The first conductive wiring layer 24 andthe second conductive wiring layer 16 cooperatively form a conductivewiring 52. In at least one exemplary embodiment, the second conductivewiring layer 16 has a thickness of about 70 μm. A cross-sectional shapeof the second conductive wiring layer 16 is substantially trapezoidal.

At block 111, referring to FIG. 12, a second cover film 60 is covered onand fills in gaps of the second conductive wiring layer 16, therebyforming the circuit board 100.

In at least one exemplary embodiment, the second cover film 60 comprisesa second cover layer 62 and a second adhesive layer 64 connected to thesecond cover layer 62. The second adhesive layer 64 is positionedbetween the second cover layer 62 and the second conductive wiring layer16 and fills in gaps of the second conductive wiring layer 16. Thesecond cover film 60 can be made of a material the same as that of thefirst cover film 40.

In other exemplary embodiments, the first dry film 20, the second dryfilm 30, and the third dry film 50 can be replaced by liquid photoresist films or fiber resin films, which are made of a photoresistingmaterial.

Referring to FIG. 12, the circuit board 11 comprises a conductive wiring52. The conductive wiring 52 comprises a first conductive wiring layer24 and a second conductive wiring layer 16. The first conductive wiringlayer 24 is formed by electroplating. The second conductive wiring layer16 is formed by etching a metal substrate 10. The first conductivewiring layer 24 and the second conductive wiring layer 16 are in directcontact and electrically connected to each other. A projection of thefirst conductive wiring layer 24 along a direction perpendicular to thecircuit board 100 and a projection of the second conductive wiring layer16 totally cover each other.

The circuit board 100 further comprises a first cover film 40 coveringand filling in gaps of the first conductive wiring layer 24, and asecond cover film 60 covering and filling in gaps of the secondconductive wiring layer 16.

With the above configuration, the second conductive wiring layer 16 isdirectly formed by etching the metal substrate 10 having a suitablethickness, thereby avoiding under etching during the etching process.Furthermore, the first conductive wiring layer 24 and the secondconductive wiring layer 16 are in direct contact and electricallyconnected to each other to form the conductive wiring 52. A projectionof the first conductive wiring layer 24 along a direction perpendicularto the circuit board 100 and a projection of the second conductivewiring layer 16 totally cover each other. Thus, a line space and a linewidth of the conductive wiring 52 can be decreased.

Even though information and advantages of the present embodiments havebeen set forth in the foregoing description, together with details ofthe structures and functions of the present embodiments, the disclosureis illustrative only. Changes may be made in detail, especially inmatters of shape, size, and arrangement of parts within the principlesof the present embodiments to the full extent indicated by the plainmeaning of the terms in which the appended claims are expressed.

What is claimed is:
 1. A method for manufacturing a circuit boardcomprising: providing a metal substrate comprising a first surface and asecond surface facing away from the first surface; electroplating themetal substrate to form a first conductive wiring layer on the firstsurface; and completely etching a portion of the metal substrate fromthe second surface to the first surface, thereby forming a secondconductive wiring layer; the first conductive wiring layer and thesecond conductive wiring layer being direct contact to each other, thefirst conductive wiring layer and the second conductive wiring layercooperatively forming a conductive wiring, thereby forming the circuitboard; wherein a projection of the first conductive wiring layer along adirection perpendicular to the circuit board and a projection of thesecond conductive wiring layer totally cover each other.
 2. The methodof claim 1, wherein the step of electroplating the metal substrate toform a first conductive wiring layer on the first surface, furthercomprising: forming a first dry film and a second dry film on the firstsurface and the second surface, respectively; treating the first dryfilm and the second dry film by an exposure and development process,thereby forming a hollow pattern in the first dry film towards the firstsurface; removing the first dry film and the second dry film; andelectroplating the metal substrate to form the first conductive wiringlayer in the hollow pattern.
 3. The method of claim 2, wherein the stepof treating the first dry film and the second dry film by an exposureand development process, further comprising: covering a photo mask onthe first dry film facing away from the metal substrate, and exposingthe first dry film and the second dry film to ultraviolet radiation,thereby causing the second dry film and an uncovered portion of thefirst dry film to be exposed under the ultraviolet radiation; removingthe photo mask and etching a remaining unexposed portion of the firstdry film, thereby forming the hollow pattern in the first dry film. 4.The method of claim 2, the first dry film has a thickness greater than athickness of the second dry film.
 5. The method of claim 4, wherein thefirst dry film has a thickness of about 75 μm, and the second dry filmhas a thickness of about 15 μm.
 6. The method of claim 1, wherein themetal substrate has a thickness of about 50 μm to about 80 μm.
 7. Themethod of claim 1, wherein the first conductive wiring layer has athickness of about 60 μm to about 70 μm, a cross-sectional shape of thefirst conductive wiring layer is rectangular.
 8. The method of claim 1,further comprising: covering a first cover film on the first conductivewiring layer and filling the first cover film in gaps of the firstconductive wiring layer.
 9. The method of claim 8, wherein the firstcover film comprises a first cover layer and a first adhesive layerconnected to the first cover layer, the first adhesive layer is betweenthe first cover layer and the first conductive wiring layer and fills inthe gaps of the first conductive wiring layer.
 10. The method of claim1, wherein the step of completely etching a portion of the metalsubstrate from the second surface to the first surface, furthercomprising: covering a third dry film on the second surface; treatingthe third dry film by an exposure process to form patterns correspondingto the first conductive wiring layer; treating the metal substrate by adevelopment process through the patterned third dry film, therebycompletely etching the portion of the metal substrate from the secondsurface to the first surface to form the second conductive wiring layer;and removing the third dry film.
 11. The method of claim 10, wherein thesecond conductive wiring layer has a thickness of about 70 μm, and across-sectional shape of the second conductive wiring layer istrapezoidal.
 12. The method of claim 1, further comprising: covering asecond cover film on the second conductive wiring layer which fills ingaps of the second conductive wiring layer.
 13. The method of claim 12,wherein the second cover film comprises a second cover layer and asecond adhesive layer connected to the second cover layer, the secondadhesive layer is positioned between the second cover layer and thesecond conductive wiring layer and fills in the gaps of the secondconductive wiring layer.
 14. A circuit board comprising: a conductivewiring comprising: a first conductive wiring layer; and a secondconductive wiring layer; wherein the first conductive wiring layer andthe second conductive wiring layer are in direct contact to each other,a projection of the first conductive wiring layer along a directionperpendicular to the circuit board and a projection of the secondconductive wiring layer totally cover each other.
 15. The circuit boardof claim 14, further comprising a first cover film covering and fillingin gaps of the first conductive wiring layer.
 16. The circuit board ofclaim 14, further comprising a second cover film covering and filling ingaps of the second conductive wiring layer.